Engine and propeller control



April 24, 1945 v FRENCH 2,374,275

ENGINE AND PROPELLER CONTROL Filed Oct. 16, 1941 2 Sheets-Sheet 1INVENTOR ATTORNEY..

AIbertHH 'mch W 4., A. H. FRENCH ENGINE AND PROPELLER CONTROL 2Sheets-Sheet 2 Filed Oct. 16, 1941 AIlierfHFrenclz ATTORNEY PatentedApr. 24, 1945 2,374,276 OFFICE ENGINE AND PROPELLER CONTROL Albert H.French, Beverly Hills, Caliifi, assignor to United Aircraft Corporation,East Hartford, Conn., a corporation of Delaware Application October 16,1941. Serial No. 415,255

5 Claims. (Cl. Nil-135.6)

This invention relates to improvements in. control means foraircraftpower plants and has particular reference to an improved control for apower plant including an engine and a constant-speed controllable-pitchpropeller.

An object of the invention resides in the provision of an improvedcontrol for an aircraft power plant of the character indicated whichrequires but a single manually operable controlled element.

A further object resides in the provision of an improved aircraft powerplant control of the character indicated which will automatically changethe propeller pitch toward a higher pitch setting upon engine failure sothat the bladesof a feathering-type propeller can be quickly and easilyturned to their feathered position before further injury is caused tothe engine by the windmilling of the propeller.

A stillfurther object resides in theprovision of an improved aircraftpower plant control means of the character indicated which is effectiveto maintain the propeller in a relatively high pitch position while theengine torque is low to thereby limit the engine speed to safe values inthe event the engine power is suddenly increased from low power oridling operation.

An additional object resides in the provision of an'improved aircraftpower plant control of the character indicated which automaticallycorrelates the engine torque with the engine speed in such manner thatthere is always a definite predetermined relationship between the torqueand speed of the engine and both-of these factors of engine operationcan be regulated in a predetermined manner by adjusting the engine thottle to control the engine power output.

Another objectresidesin the provision of aircraft power plant controlmeans which can be readily utilized to synchronize the speed of thengines of a multi-engine aircraft.

Other objects and advantages will be more particularly pointed outhereinafter or will become apparent as the description proceeds; j

In the accompanying drawings, in which like reference numerals areusedto designate similar parts throughout, there is illustrated asuitable mechanical arrangement for the purpose of disclosing theinvention. The drawings, however, are for the purpose ofillustrationonly and are not to be taken as limiting or restricting the.invention since it will be apparent to those skilled trollable pitchpropellers.

Fig. 2 is a somewhat schematic sectional view of the improved controlmeans.

Fig. 3 is a sectional view through the forward portion of an aircraftengine showing the ap-' pilcation thereto of a torque responsivemechanism which constitutes a portion of the control means illustratedin Fig. 2.

Fig. 4 is a somewhat schematic sectional view of an alternativeconnection between the torque responsive means and the propeller pitchregulating governor illustrated in Fig. 2, and

Fig. 5 is a diagrammatic illustration of' the improvedcontrol means whenadapted to synchronize the speed of two or more engines.

Referring to the drawings in detail, and particularly to Fig. 1, thenumeral lllgenerally indicates an aircraft engine such as a radialaircooled type of engine ordinarily employed for this purposealthough'the invention is in no way limited to any particular type ofengine. The numeral l2 generally indicates a controllablepitch propellerdriven by the engine I0 which propeller may be a hydraulically actuatedfeathering-type well known to the art and particularly illustratedanddescribed in United States Patent No. 2,174,717, issued October 3, 1939;to Frank'W. Caldwell et al. for Multi-position con- The pitch of thepropeller I2 is regulated by a speed responsive governor generallyindicated at M and the power of the engine is controlled by a throttlel6 located in the engine intake I8 and controlled by manually actuatablemeans including the link 20. The

numeral 22 generally indicates a torque responsive mechanism ordinarilyreferred to in the art as a torque meter, carried-on the front end ofthe engine l0 and operatively associated with the transmission gearingfor the propeller as will presently be described.

In the arrangement illustrated, the governor I4 is mounted on the enginenosepiece 26 and is 1 1 driven from the engine by a suitable gear train,

in the art that various changes in the illustrated arrangements may beresorted to without in any way exceeding the scope of the invention.

In the drawings, Fig. 1 is a somewhat schematic elevatlonal view of afragmentary portion of an aircraft power plant showing theappllcation'of control means arranged according to the inventionthereto.

not shown. This governor includes a pair of centrifugally actuatedfiyweights 26 actin on a valve stem 28 and opposed by a speeder spring30. The counterweights and the speederspring move the valve stem inaccordance with variation in engine speed and cause the valve to controlthe' connection .of the propeller pitch changing motor with a source'offluid under pressure and a drain channel thus causing the propeller 1pitch to vary in a manner opposing any change in, englnespeed. One endof'the spring 30 bears against an adjustable abutment 32 which may bemoved to vary the loading on the speeder sprin and thereby alter thespeed setting of the governor. a v

As is particularly'shown in Fig. 3, the engine crankshaft 34 isconnected with thepropeller shaft 36 through a planetary reduction gearincluding the ring gear 38 drlvinsly'connected with permit highpropeller the crankshaft, the planetary gears 40 carried on the cage42-drivingly connected with the propeller shaft 30 and the reaction gear44 with which the planetary gears 40 mesh in addition to the ring gear38. With this arrangement the force exerted on the reaction gear 44 is adirect indication of the torque transmitted to the propeller shaft 06.The reaction gear is provided with a double ended lever member 48 theends oi! which are operatively connected, by means suitable links orrods 48 and 50, with respective pistons 52 and 54 reciprocable inrespective cylinders 58 and 58 carried by the engine nosepiece 24.Hydraulic fluid under pressure is supplied to the spaces between thepiston and the closed ends of the cylinders from a fluid pressure-line00 and conduit 62 interconnecting the spaces in the two cylinders. Thefluid supply is controlled by a valve 64 operated by one of the pistons,for example the piston 54, in such a manner that the fluid underpressure maintains the pistons spaced a substantially constant distancefrom the closed ends of the respective cylinders. The pressure of thefluid in the spaces between the pistons and the closed ends of thecylinders will then constitute a direct indication of the torque appliedto the propeller shaft and this pressure may be indicated, in torqueunits if desired, by-a suitable gauge 86.

. In order to correlate the engine torque with the engine weed, aconduit 60 is led'irom the system containing the fluid at, torqueindicating pressure to the interior of a cylinder I0 within which themovable abutment 32 for the speeder spring 30 is reciprocably received,the conduit being led to the space between the closed end of thiscylinder and the movable abutment.

.With this arrangement, the torque applied by the engine to thepropeller shaft. is imposed through the fluid mediumon the abutment 32in a manner such that the speed setting of the governor is adjustedindirect relation to changes in engine torque. That is, when the enginetorque increases the governor is changed to a higher speed setting,causing, by a decrease in the pitch angle of the-propeller, ifnecessary, a taster engine speed. This provides an operatingcondition-under which the engine power can be varied throughout theentire operative range by manual adjustment of the engine throttle i0and it is not necessary to manually adjust the governor in order toobtain any desiredengine power output. Several advantages accrue fromthis method of operation. For one. the engine can'be adequatelycontrolled by a single manually operated control element namely thethrottle, for another, the engine and propeller are automatically setfor optimum operating conditions for different maneuvers. For example,ior take-oi! at high engine power, the propeller pitch is'reduced enoughto speed and the highest pitch setting compatible with the desired speedand the allowed engine power output thereby permitting the propeller todevelop the maximum static thrust 101' the takeit. This operatingcondition also provides a desired speed and blade pitch setting forcruising since, after the complete and the airplane is leveled off andcruising conditions initiated, the engine. power is greatly reduced byclosing the throttle with a consequent reduction in the torque deliveredat takeoil! weed. The relationship between the torque meter and thegovernor can-be Ila-arranged that a relatively small throttling of theengine from wide open throttle will produce a considerable increase inthe propeller blade pitch angle thus causing the powerplant to operateat a relatively slow speed and large throttle opening which is theoptimum cruising condition especially from the point or view of minimumfuel consumption.

The proper coordination between engine speed and engine torque may beobtained in some installations by properly proportioning the area of theabutment 32 to the strength of the spring 30 and the pressure of thefluid in the conduit 00. In case it should be impossible in certainother installations to accomplish the proper torque inFig.5.

scribedaboveanddrivesa veloped by the engine speed ratios by the correctevaluation of the above mentioned factors, some other arrangements forchanging the governor setting may be provided, such for example, as thatillustrated in Fig. 4. In this arrangement, the fluid conduit 68,instead of being connected directly with the abutment cylinder I0 isconnected to one end of the cylinder I2 of a servo-motor disposedbetween the torque meter and the governor. Within the cylinder I2 thereis a reciprocable piston I4 connected by a rod 16 with a cam I0 whichcontacts a cam follower 80 carried upon the projecting end of a stem 82extending from the abutment 02 out of the cylinder I0 through the closedend of this cylinder. With this arrangement, movements of the piston I4effected by pressure of the fluid in the conduit 60 will cause the cam10 to.

30. Movement of the piston 14 by the pressure fluid maybe resisted by acompression spring 84 surrounding the rod I6 and bearing at one endagainst the piston and at the other end against an etzlutment member 80secured to the cylinder The fact that the track of the cam 10 may bevaried almost infinitely gives .to this form or adjusting mechanism agreater flexibility which renders it possible to properly coordinate thespeed setting adjustment of the governor to the engine torque forpractically any installation.

Since this arrangement maintains the engine power at a deflnitepredetermined relationship to engine speed, an indication of enginespeed would also indicate the horse powerbeing deand, if desired, atachometer could be used calibrated directly in engine power units.

The improved control may be utilized to synchronize the speeds of two ormore engines by a suitable arrangement such as that illustrated In thisarrangement the engine A iu'nctions as the master engine and'the speedoi the engine B is synchronized with that oi the engine A. The engine Ais provided with a control such as has been described above and inaddition drives an electric current impulse generator 00. The engine Bis also provided with a control as desimilar current impulse generator00. The two generators 00 and 00 are portions oi. an electricaldiflerential or 8elsyn" unit I! the rotatable portion of which isdrivingly connected with a shait 04 screw threaded into the plunger 00or a needle valve device comprising the valve member 00 and the valveseat casing 00. A conduit I00 leads from the torque meter of thecontrolledenginetotheneedlevalveandadraln conduit I02 leads from theneedle valve to a fluid reservoir. I04 which may be an engine sump oroilstoragetank.

v If oil is bled from the torque meter 22b of the controlled motor thisfluid will be made up to a certain extent by the pressure fluid enteringthe torque meter from the pressure line 60, the extent of the make updepending upon the restriction of the fluid pressure line 60 and therestriction of the bleed. With this continuous replenishment of thefluid in the torque meter and with the needle valve 96 arranged tobleed,.at its maximum capacity, fluid from the torque meter somewhatmore rapidly than it can be replenished from the fluid pressure line,the fluid pressure in the torque meter 22?) acting on theabutment 32' ofthe respective engine governor or the piston 74 of the respectiveservo-motor can be regulated and will in turn regulate the speed settingof the respective governor. The opening of the valve variations in thetorque of said engine, including 96 is controlled by the electricdifferential device 92 in such a manner that if the speed of the controlled engine B lags behind that of the master engine A the needlevalve 96 will be closed thereby increasing the pressure in the torquemeter 22b of the controlled engine and resulting in an increased speedsetting of the governor l lb and a consequent increase in the speed ofthe controlled engine until the speed of the master engine is matched.If the speed of the controlled engine exceeds that of the master engineA the needle valve 96 would be opened by the electric differentialdevice thereby reducing the pressure in the torque meter 22b resultingin a lowered speed setting of the governor speed of the controlledengine until the speed of the controlled engine matches the speed of themaster engine. Thus the improved control device with the addition ofvery few elements can be adapted to synchronize the speed of acontrolled engine to a master speed.

While a suitable mechanical embodiment has been hereinabove describedand illustrated in the accompanying drawings for the purpose ofdisclosing the invention, it is to be understood that the invention isnot limited to the particular embodiment so described and illustratedbut that such changes in the size, shape and arrangement of' the variousparts may be resorted to as come within the scope of the sub-joinedclaims.

Having now described the invention so that others skilled in the art mayclearly understand the same, what it is desired to secure by LettersPatent is as follows:

1. In combination with a reference speed device, means for synchronizingthe speed of a power plant, including an engine, a load varying device,a governor controlling said load varying device and means for changingthe speed setting of said governor, with said reference speed device,said synchronizing means comprising, a, hydraulic torque responsivedevice operatively associated with said engine, means operativelyconnecting said torque responsive device with the governor speed settingmeans to control the speed of said power plant in response to torquevariations, a valve for regulating the fluid pressure in said torqueresponsive device and means for controlling said valve comprising agenerator driven by said power plant, a generator driven by saidreference speed device and an electrical differential unitoperativelyassociated with said valve and connected with saidgenerators.

2. In combination with a power plant including an engine, a controllablepitch propeller and a pitch controlling speed governor mounted on astationary support, a throttle for varying the i torque of said engine,manually operable means Nb and a decrease in the sib1echamber device tofor controlling said throttle, means responsive to an expansible chamberdevice, applying pressure to hydraulic fluid in proportion to the torquevalue, a speeder spring for said governor, means for adjusting the speedsetting of said governor comprising an' expansible chamber device forchanging the force exerted by saidspeeder spring, an hydraulic lineoperatively connecting the torque responsive expansible chamber devicewith the speeder spring adjusting expansible chamber device to changethe speed setting of said governor in accordance with variations inengine torque.

3. In combination with a power plant including an engine, acontrollable-pitch propeller, and a speed governor controlling propellerpitch changes, and a throttle for said engine, manually operable meansfor controlling said throttle, means responsive to variations in the.torque of said engine, and means operatively connecting said torqueresponsive means with said speed governor to change the speed setting ofsaid governor in accordance with variations in engine torque,

and comprising a'cam and cam follower the face of said cam being shapedto provide a predetermined relationship between the torque developed bysaid engine and the speed setting of said governor.

4. In combination with a power plant including an engine, acontrollable-pitch propeller, a pitch controlling speed governor, and athrottle for varying the torque of said engine, a unitary speed andtorque control comprising manually operable means for controlling saidthrottle, means responsive to variations in the torque of said engine,including an expansible chamber device, applying pressure to liquid inproportion to the torque value, a speeder spring for said governor,means for adjusting the speed setting of said governor comprising, acanr device, and an expansible chamber device changing the position ofsaid cam device for changing the force exerted by said speeder spring, aliquid line operatively connecting the torque responsive expansiblechamber device withthe speeder spring adjusting expanchange the speed ofsetting of said governor in accordance with variations in engine torque,said cam device being shaped to provide a predetermined relation betweenthe torque developed by said engine and the speed setting of saidgovernor.

5. In combination with a reference speed device and a power plant,including an engine, a

load varying device, a, governor controlling said load varying device,and means for changing the speed setting of said governor, means forsynchronizing the speed of said power plant with the speed of saidreference speed device comprising, a hydraulic torque responsive deviceoperatively associated with said engine, means operatively connectingsaid torque responsive device with the governor speed setting means tocontrol the speed of said power plant in response to torque variations,means for maintaining the supply of fluid in said torque responsivedevice, a valve for regulating the fluid pressureap'plied by said torqueresponsive device to said governor-setting means, and means forcontrolling said valve comprising, a generator driven by said power tordriven by said reference speed device, and an electrical differentialunit operatively associated with said valve and connected with saidgeneratOl'S- v v ALBERT. H. FRENCH- plant, a genera-

